The cause(s) of neuropsychiatric systemic lupus erythematosus (NPSLE) remains an enigma. Although numerous reports of associations between specific autoantibodies and CNS manifestations have been published, serum levels of none of these autoantibodies has consistently shown a high degree of sensitivity and specificity for NPSLE. Recently it has been demonstrated that immune complexes containing nucleoproteins become internalized and stimulate Toll Like Receptors (TLRs) to produce type 1 interferon (IFN). IFN has previously been implicated in NPSLE and high concentrations of IFN are known to cause neuropsychiatric symptoms similar to NPSLE. We therefore hypothesize that cell death coupled with the release of nucleoproteins results in the formation of immune complexes that stimulate TLRs to produce high local concentrations of type 1 IFN (and perhaps other cytokines) in the central nervous system (CNS) thereby causing NPSLE. The specific aims of the proposal are: To compare the frequency and activity of interferogenic (IFG) complexes in the serum (and CSF) of patients with and without NPSLE. The ability of serum from NPSLE and non NPSLE, matched for activity and other parameters to stimulate IFN and other inflammatory cytokines from mixed peripheral blood mononuclear cells as well as from cultured human microglia will be compared. A requirement for apoptotic or necrotic cells as a source of antigens will be tested and the ability of NPSLE serum to induce both cell death of neuronal targets followed by IFG immune complex formation will be examined. To determine the autoantibody specificities, nature of the antigens and TLR pathway responsible for the IFG activity. The autoantigens, their nucleic acid composition will be defined by immunochemical techniques and mass spectrometry as required. The cellular origin of cytokines will be determined by positive and negative selection. Identification of specific TLRs will be achieved by selective inhibition of endosomal TLR using oligonucleotides or siRNA. These studies are expected to lead to a new understanding of the pathogenesis of NPSLE that accounts for both autoantibodies with 'cytotoxic' function as well as autoantibodies that form nucleoprotein complexes that are now known to stimulate IFN and other pro-inflammatory and neuromodulatory cytokines. The cause of most cases of lupus affecting the brain is unknown, but there is good evidence to suggest that certain types of antibodies may play a role. Here, we test the idea that the sequential action of different antibodies that cause tissue injury followed by antibodies that capture antigens and enter the cell, causes the release of proteins called cytokines that alter brain function. [unreadable] [unreadable] [unreadable]